Generally, data transfer systems include a data bus capable of transferring data between a master device and one or more peripheral devices. In a traditional data transfer system, the master device addresses each of the peripheral devices with an address preceding any data which it desires to send to the peripheral devices. The addresses of the peripheral devices are usually predetermined prior to operation of the data bus and are known to the master.
In newer automated systems, the address of the peripheral devices are unknown prior to operation of the data transfer system. Upon start up of the data transfer system, there is an initialization period in which each of the peripheral devices communicate to the master controller the address and other device-type information. These newer devices are far more complex and sophisticated than the traditional data transfer systems, however, they allow for the ease of operation from an users point of view. This initialization period is very complicated and requires a high degree of accuracy. If the data transfer system is initialized incorrectly, then, the subsequent communications may be lost.
It is well known in the data communications sector that there is a push for a high speed data transfer system which is capable of transferring more data with greater efficiency. Additionally, there is concern that the data transfer system generate minimal radio frequency interference (RFI) and electromagnetic interference (EMI) radiation. One way to reduce the amount of RFI and EMI radiation is to reduce the amplitude of the signal level on the data bus from the traditional 5 volts peak-to-peak signal level to 0.5 volt peak-to-peak. This reduction in the amplitude significantly reduces the amount of radiation generated by the data transfer system. Secondly, in order to create a low amplitude data system the signals generated by each of the devices connected to the data bus are heavily filtered in order to remove the harsh peak of the signal. This filtering elongates the rise and fall times of the transitions on the data bus causing variances in the signal transmitted between the master peripheral devices. Third, the high speed low amplitude data bus in which the master peripheral devices are separated by distance greater than a meter the capacitance of the physical cables of the data bus cause variable and long delay times in the transition of data between the master peripheral devices.
In order to preserve the required integrity of a automated complex data transfer system which includes a high speed low amplitude data bus and a separation of peripheral and master controllers by distances up to 20 meters, a highly accurate initialization in bus arbitration method and apparatus need to be developed such that the integrity of the data transfer system is not interfered with by noise or variances in communications during the initialization period.